Volcanic super eruptions regularly tore up the surface of Mars billions of years ago, altering the planet's climate for decades and creating scars that are still visible today, a new study has found.
A team of American geologists found evidence that large craters visible in satellite images of northern Mars' Arabia Terra region were not created by asteroids, as some had originally believed, but by massive volcanic eruptions that could blast billions of tons of gas and molten rock up into the atmosphere.
Better known as calderas, these craters are essentially the remnants of once-powerful explosive super volcanoes, and they have more irregular shapes than their asteroid-created counterparts. But since those powerful eruptions are believed to have taken place some 4 billion years ago, finding conclusive evidence about their nature required rather forensic methods.
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The scientists looked for traces of volcanic ash and modelled how it would disperse after such eruptions and where it would deposit. Then, they looked at high-resolution images taken by NASA's Mars Reconnaissance Orbiter to see whether the patterns matched their expectations.
"At that point we said, 'OK, well these are minerals that are associated with altered volcanic ash, which has already been documented, so now we're going to look at how the minerals are distributed to see if they follow the pattern we would expect to see from super eruptions," study co-author Alexandra Matiella Novak, a volcanologist at the Johns Hopkins Applied Physics Laboratory in Laurel, Maryland, said in a statement. The new research built on Matiella Novak's previous studies of volcanic ash depositions in other regions of Mars.
What the researchers found in the images matched the models. The ash spread downwind, eastward from the seven calderas revealed in the Mars Reconnaissance Orbiter images. The deposited ash was traceable thousands of miles away from the craters, the layer thinning out farther away from the source.
"We're actually seeing what was predicted, and that was the most exciting moment for me," study co-author Jacob Richardson, a geologist at NASA's Goddard Space Center in Greenbelt, Maryland, said in the statement.
The supervolcanoes, likely active during a period of 500 million years some 4 billion years ago, spewed massive amounts of water vapor, carbon dioxide and sulfur dioxide into the atmosphere of Mars, throwing the planet's climate off balance for decades.
"Each one of these eruptions would have had a significant climate impact — maybe the released gas made the atmosphere thicker or blocked the sun and made the atmosphere colder," study lead author Patrick Whelley, a geologist at NASA Goddard, said in the statement. "Modelers of the Martian climate will have some work to do to try to understand the impact of the volcanoes."
The last supervolcano eruption on Earth took place 76,000 years ago in Sumatra, Indonesia. But terrestrial calderas, dozens of miles wide, are spread around the globe in known tectonically active regions, where the majority of smaller but still active volcanoes also reside today.
The strange thing about the Martian Arabia Terra, however, is the fact that it doesn't show traces of smaller volcanoes.
The scientists speculate that calderas on Earth may have been eroded over billions of years or moved around the globe with the shifting continents. These types of explosive volcanoes could also exist in regions of Jupiter's moon Io or could have been clustered on Venus, the scientist said.
Earlier this year, scientists from the Planetary Science Institute in Tucson, Arizona, found evidence that Mars might still be volcanically active today. Most of the Red Planet's volcanic activity, however, occured in the era of the supervolcanoes some 4 billion years ago. Mars' 13.6-mile high (21.9 km) Olympus Mons, the biggest volcano in the solar system, is believed to have last erupted about 25 million years ago.
The study was published in the journal Geophysical Research Letters in July 2021.
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